1. Field of the Invention
The present invention broadly relates to a method for separating non-fibrous particulate from fibers. More particularly, the present invention provides a method for separating elastomeric particulates, such as crumb rubber, from fibers, such as polyester fibers.
2. Description of the Prior Art
The disposal of discarded rubber vehicle tires, especially for cities, states and industries throughout the United States, has been a problem ever since transportation first began to use tires. Billions of discarded tires occupy landfills and stockpiles. For many years, governmental bodies as well as industrial corporations have worked to reduce the growing stockpile of discarded tires. Some states even charge $1.00 to $2.00 on each new tire sold in order to fund disposal and/or disposal research.
Indiscriminate discarding of rubber vehicle tires poses an environmental and health problem. Waste tires provide breeding grounds for insects and rodents. They are not biodegradable and are difficult to store in landfills because their hollow toroidal shape prematurely fills a dumpsite.
The difficulty of discarding worn out rubber tires has led to investments in disposal technologies so that tires will take up less volume when stored in landfills. It has also led to an increased demand for an efficient and cost-effective method of recycling tires to avoid the disposing of worn out tires in landfills.
Recycling of rubber tires is difficult because of the problems associated with separating tires into their multiple components. A tire typically comprises rubber tread and rubber-coated sidewalls. Both natural and synthetic rubbers, including natural rubber, styrene, butadiene (SBR) rubber, polybutadiene rubber, butyl rubber and polyisoprene rubber are used in tire manufacturing. In order that a tire may possess superior strength and wear resistance, the rubber is usually vulcanized, resulting in a toughness for the tire that contributes to its associated indestructibility. Also, a used tire is typically reinforced with belts of steel wire and reinforcing fabric or fiber. These reinforcing components are typically wrapped and bonded together by rubber layers to form a tough, durable tire, all of which impede it""s recycling.
The majority of the techniques used to recover recyclable components from waste tires require initial physical processing, such as shredding or cryogenic crushing or pulverizing, followed by further refining with a secondary process, such as converting the materials into a reusable form by chemical digestion, mechanical reclamation, destructive distillation, etc. In cryogenic crushing or pulverizing, liquid nitrogen is used to lower the temperature of the tire to about xe2x88x92300xc2x0 Fahrenheit. At such low temperatures, rubber hardens and is easily fractured into tiny granules or particulates, leaving steel wire and reinforcing fibers relatively unaffected. The steel wire is removed by electromagnetics and the reinforcing fibers are removed by sieving. The cost of cryogenic processing is relatively high, and typically only about 50% by weight of the rubber granules are recovered. The remaining rubber granules and their admixed or adherent wires and fibers are usually disposed of in landfills.
Young in U.S. Pat. No. 1,321,201 discloses a process for reclaiming rubber and cotton from waste which utilizes a system in which the waste to be separated is first wetted, then formed into a sheet between rollers, before being torn into its component by a high speed picker.
Horton et al. in U.S. Pat. No. 2,729,856 teach a process for separating fibrous vegetable materials into pith and fiber portions. These methods require a hackle and hammer action to free the fibrous material in conjunction with the simultaneous action of water jets.
Therefore, what is needed and what has been invented is a method to avoid the deficiencies of the prior art in recovering recyclable components from waste tires by providing an inexpensive and effective method for recovering rubber particulates from a pulverized tire mixture. What is further needed and what has been invented is a method for separating particulate rubber (e.g. crumb rubber) from fibers (e.g. polyester fibers).
The present invention accomplishes its desired objects by broadly providing a method for separating non-fibrous particulates from fibers in the substantial absence of water comprising the steps of: (a) providing a pulverized mixture comprising non-fibrous particulates and fibers; and (b) contacting the pulverized mixture of step (a) with a plurality of revolving mixture-engaging structures (e.g., a plurality of revolving spikes) to cause the revolving mixture-engaging structures to engage the fibers and separate the fibers from the non-fibrous particulates.
The present invention also accomplishes its desired objects by further broadly providing a method for separating elastomeric particulates from fibers in the substantial absence of water comprising the steps of: (a) providing a pulverized elastomeric mixture comprising elastomeric particulates (e.g. plastic particulates, rubber particulates, etc.) and fibers (e.g. natural and/or synthetic and/or metal fibers, etc.); (b) contacting the pulverized elastomeric mixture of step (a) with a first revolving mixture-engaging structure (e.g., a plurality of first revolving spikes) to cause the first revolving mixture-engaging structure to remove fibers and separate elastomeric particulates from the pulverized elastomeric mixture, with the removed fibers having residual elastomeric particulates; and (c) propelling the removed fibers of step (b) against a second revolving mixture-engaging structure (e.g., a plurality of second revolving spikes) to cause the second revolving mixture-engaging structure to engage the removed fibers and separate residual elastomer particulates from the removed fibers.
The present invention more specifically provides a method for separating crumb rubber from polyester fibers in the substantial absence of water comprising the steps of: (a) introducing (e.g. gravity feeding, etc.) a pulverized mixture of crumb rubber and polyester fibers into a separation zone containing a plurality of mixture-engaging structures (e.g., a plurality of revolving spiked cylinders) to separate a portion of the polyester fibers from the pulverized mixture and produce crumb rubber containing residual polyester fibers; and (b) removing the residual polyester fibers from the crumb rubber.
The present invention further accomplishes its desired objects by broadly providing an apparatus for separating non-fibrous particulates from fibers in the substantial absence of water comprising a housing, and a plurality of cylinders rotatably mounted within the housing with each of the cylinders supporting a mixture-engaging structure. A grid-rod assembly is supported by the housing and situated in proximity to the cylinders supporting mixture-engaging structures. A pulverized mixture is disposed in the housing. Preferably, the pulverized mixture is produced from vehicle tires and comprises fibers and crumb rubber. The crumb rubber preferably comprises particles having an average maximum dimension ranging from about {fraction (1/512)} inch to about xe2x85x9 inch.
It is therefore an object of the present invention to provide an apparatus and a method for separating non-fibrous particulates from fibers.
It is another object of the present invention to provide a method for separating elastomeric particulates from fibers.
It is also another object of the present invention to provide a method for separating crumb rubber from polyester fibers.